With Timeline rolling out, I want to take the chance to clean up my Facebook account. I could delete unwanted friends I added willy-nilly one by one, but that would take forever. Is there an easy way to do it?

Yes, there is, but you have to do it before you start using Timeline. FacebookDeletes is a Greasemonkey script for Firefox that will let you delete multiple Facebook friends with a simple checkbox. With the script installed, you need to head over to your friends page where you'll see a "Facebook Delete Friends" button. Now, you just need to check the boxes of the friends you DON'T want to delete.

If you already have Timeline installed, there doesn't seem to be a clear way to delete a large group of friends at once, so if you want to do some housekeeping, you should do it now.